Tubular hot-air heater



TUBULAR HOT-AIR HEATER 2 Sheets-Sheet 1 Filed March 4. 1943 Il lll .Il

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.June 22,-1948 H. .|.V DE N. MecoLLuM 2,443,920'

l n muuu nor-'un mmm i v mea uarcn 4, 194s Y -2 suma-snug 2 Patented Jene 22, 194s TUBULAR HOT-AIR HEATER -Henry J. De N. McCollum, Chicago, Ill.; Thelma McCollum, executrix of said Henry J. De N.

McCollum, deceased, assigner to Stewart-Warner Corporation, Chicago, lil., a corporation of y Virginia 'A Application March 4, 1943, Serial No. 477,908

My invention relates to heaters, and more par ticularly to heaters of the internal combustion type.

Internal combustion heaters of the kind to y which. my invention pertains are commonly used in aircraft, and are commonly supplied with Ventilating a-ir by a raminto which atmospheric air is directed by the forward motion of the plane. In some aircraft installations, such heaters are supplied with Ventilating air by blowers,"4 and blowers, rams, or any other suitable air supply means may beV utilized where my heaters are used for heating spaces other than the cabins or other enclosed parts of airplanes. In many instances, however, the pressure availableto force the Ventilating air through the heater is limited, and in aircraft installations particularly, it is desirable to reduce to a minimum the resistance or the heater to ow of Ventilating air there-,- through.

An object of my invention is to provide a heater which ofiers a minimum of resistance to flow of Ventilating air therethrough.

Another object of my invention is to provide a heater wherein substantially all of the resistance to iiow of Ventilating air is frictional rei sistance between the air and the heating surfaces,

so that a maximum amount of heating surface may be traversed by fthe Ventilating air without increasing the resistance of the heater.

Another object of my invention is to provide 4 claims. (ci. 12s-116) a heater wherein the passages for the ventilating air are free from shoulders, pockets, and other means which would cause abruptchanges in direction oi' air ilow, or which would facilitate the formation of eddy currents or low pressure areas,

the line 6--5 of Fig. 1; and

Fig. 3 is an end elevational View looking at the left-hand end of the heater shown in Fis. l.

The heater shown in Figs. 1, 2, and 3 is con- 2 nected to a single air inlet |00 which supplies both the combustion air and Ventilating air for the heater.Y The inlet |00 may be connected with a ram, blower, or other suitable source of air supply. This heater has an outer Venturi shaped casing |02 enclosing generally cylindrical, but longitudinally curved, walls |04, |06, and |08, and which are spaced from each other and from the casing |02 to form the combustion chamber and gas passage and to form passages for ventilating air and combustion air.

Part of the air supplied by the inlet |00 enters the combustion air passage |l0 formed by the wall |08 and flows from the right-hand edge of this passage into a pipe ||2 extending through the casing |02 and connected to the air inlet of a carburetor, indicated generally by reference character ||4. This carburetor has the lusual Venturi tube H6l provided with a fuel jet ||8 supplied with fuel from a float bowl |20 connected by pipe |22 to any suitable `source of fuel. A pipe |24 connects the upper part of the float bowl |20 with the interior of the pipe ||2 lso that the pressure difference between the pipe H2 and the throat of the venturi| ||6 is available to lift the fuel from the float bowl to the jet I I8 and discharge this fuel into the Venturi tube to form a fuel and air mixture therein.

An induction tube |26 is connected to the outlet end of the Venturi tube ||6 and extends through casing |02 and wall |04 into the right-hand or combustion chamber end of an annular space |28 between the curved' walls |04 and |06, The induction tube |26 has a preheating portion |30 located in the combustion chamber and curved about the axis thereof, the outlet end |32 of this tube being arranged to discharge combustible mixture tangentially of the annular combustion chamber to form a ring of ame therein as described and claimed in my copending application Serial No. 477,080, ii-led February 25, '1943, now Patent No. 2,433,618, granted December 30, 1947. This preheating portion |30 of the induction tube may be made of any desired length to give the requisite preheating for the particular fuel with. which the heater is designed to operate.

The combustible mixture entering the combustion chamber is ignited by the electrical igniter |34 which may be 0f the same type and may be arranged as claimedin my copending application Serial No. 478,258, filed- March 6, 1943, and issued as Patent No. 2,417,604 on March 18, 1947.

The hot gases formed in the combustion cham-` ber flow lengthwise of the space |28 in a somewhat helical pathand give up their heat to the walls |04 and |002 The cooled gases are llnally bolted or otherwise secured. The right-hand ends discharged -to atmosphere through an outlet of the walls |04 and |00 are attached to the leftand any ksuitable exhaust pipe connected therehand endI of the muiiler |00 and spacing bars |18 with. l and and brackets |00. |02. |84, and |00 posi- An annular and generally conical muiller s tion and secure Ithe right-hand ends of the tube forms the right-hand wall of the combustion( |00 and muilier |00 in the right-hand end of the chamber and comprises a shell |40 containing casing |023"v Y sound absorbing material |42, such as stainless It'will thus be seen that I have provided a.`

steel wool or glass wool. Openings |44 in the end y lightweight, highly eillcient heater oifering a minwall |46 of this muler acoustically connect the 10 imum resistance tog'the ow of air therethrough, interior of the muiiier directly with the coilnbusfl so that a relatively low source of air pressure is tion chamber. whereby sound created in this capable oi causing the Ventilating air to traverse chamber may pass into the muffler and be aba maximum heating, surface. @These advantages sorbed. The annular and longitudinally curved are obtained in a heater which can beeasily manwalls |48 and |00 of this mufiier shell constitute 1s ufactured of ccnventionalmaterials and which y in effect continuations of the walls |04 and |00., is suillciently sturdy to give long and trouble-free respectively.

The annular space |28 which provides the output, and low resistance to air flow, this type o1 combustion chamber and passage for the gases heater is particularly adapted for' aircraft use, flowing therefrom. issurrounded by an annular 20 but is not limited to such use and is capable of ventilating air passage |02 formed between the general application. casing |02 and walls |00 and |418. This passage While I have illustrated and described a prein cross section is substantially Venturi-shaped, ferred embodiment of l my invention, it is to be es clearly ShOWn in Fi8 4, and has e Short e011- understood that my invention is not limited to the Atracting inlet end |54 leading to a long` throatse particular details shown and described, but may like portion |06 discharging into a. haring outlet assume numerous other forms, and that the scope portion |58 whereby this passage offers a minici my invention is defined in the following claims. mum of resistance to thefiow of air therethrough; I I claim: Y Furthermore, the air flow is at a maximum ad- 1. A heater of the class `described comprising jacent the hotter portions of the wall Y|00 and 30 a plurality/of tubular walls spaced from each absorbs a maximum of heat therefrom. In other and/arranged coaxially, the outermost two order Vto increase the transfer of heat from theB of said walls forming a Ventilating air passage wall |00 to the Ventilating air, this wall has aftherebetween. the innermost pair of walls formfiXed thereto L-Sheped Strips |60 having radially ing a second Ventilating air passage therebetween, projecting nhs |82 which are scrubbed by the 95 said walls forming a gaspassage and combus- Ventilating air as it passes through the throat- -tionchamber between said air passages. means like portion |62 of this Ventilating air passage. forming an inlet for said Ventilating air passages,

A second annular, Ventilating air passage |84 means for supplying a combustible mixture to said is formed between the wall |06 lof the combustion gas passage at the end thereof opposite Seid all chamber and gas passage and the wall |08 of the 40 inlet, a carburetor for supplying said combustible combustion air passage. The Ventilating air mixture, and a combustion air passage for said passage |84 is annular and has the same Venturicarburetor formed by said innermost annular like cross section of the Ventilating air passagev wall and receiving air from said air inlet.

Just described. L-shapedstrips |60 are attached 2.. A heater of the class described comprising to the wail |06 of the gas passage |28 and have in- 45 means forming an annular combustion chamber, wardly projecting fins |68 to facilitate the transan annular muiller forming an end wall of said ier of heat from the wall |06 to the Ventilating combustion chamber, means providing a gas pasair passing through the passage |04. sage communicating with said combustion cham- Frcm the foregoing. it will be apparent that the ber. means providing a Ventilating air passage Ventilating ail passages are shaped to oder mini- 5 surrounding said gas passage, combustion chammum resistance to the flow of air therethrough. ber, and muiller, andvmeans providing an air service. Because of its light weight, high heat The combustion air-passage ||0 is not ideally passage inwardly of said gasA passage, combusshaped, from the standpoint of offering resistance tion chamber, and muiiler, said air passages being to flow ci.' combustion air therethrough. The of Venturi-like longitudinal section.

volume of combustion air flowing through the Y 3. A heater of the class described comprising a passage ||0, however, is relatively small compared lplurality of tubular walls spaced from each other to the cross sectional area of( this passage, so that I and arranged .coaxially, the outermost two of said the shape of the passage ||0 is relatively unimwalls forming a Ventilating air vpassage therebeportant. I wish to point out, however, that even tween, the innermost pair ,of walls forming a this passage is free from shoulders or other abrupt SeeOnd Ventilating air passage therebetween. changes in the contour of its walls, and that the Said walls forming a ses passage and combustion waus of this passage are smoothly curved and.V chamber between said air passages, said air pasoier little resistance of air therethrough. Sages being of Venturi-like longitudinal section, The walls of the gas'pssage |20 are also designed means, forming an air inlet for said Ventilating to offer little resistance to the flow 'of the gases 55 all' PaS-tages. and means for supplying 60mof combustion .imm the combustion chamber to bustible mixture t0 Said gas passage at the end the outlet |30. thereof opposite said air inlet including a car- As clearly shown in Fig. 1, the left-hand ends buretor and a combustion, air passage for said of the walls |04 and |00 are welded or soldered carburetor formed by the innermost annular wall together, and supporting brackets |10 are welded 70 and receiving air from said air inlet.

or soldered at spaced intervals to the left-handk 4. A heater of the class described comprising end of. the wall l |04. These brackets v|10 are a plurality of tubular walls spaced from each bolted to U-shaped straps |12 and |14 which other and arranged coaxiallythe outermost two serve to support the walls |04, |06, and |08 in the o'f said walls forming a Ventilating air passage casing |02 to which the U-shaped straps |12 are 75 therebetween. theinnermost pairoi' walls forminga second Ventilating air passage therebetween, said walls forming a sas passage and combustion chamber between said air passages. said air pas sages being o! Venturi-like longitudinal section, means forming an air inlet i'cr said Ventilating air passages, and means for supplying. a combustible mixture to said gas passage including a carbur'etor and a. combustion air passage for said carburetor formed by the innermost annular wall and receiving air from said air inlet.

HENRY J. DE N. McCOLLUM.

REFERENCES CITED The following references are oi' record in the iile of this patent: s

Number UNITED STATES PATENTSA Name Date Schaffer July 17, 1900 Cramer Apr. 22, 1930 Beal et a1. Oct. 28, 1930 Baetz Mar. 15, 1932 Kruse Nov. 26, 1935 Herbster Dec. 3, 1935 Grill et al. v Dec. 27, 1938 Rock May 16, 1939 Herbster Mar, 23, 1943 Case July 27, 1943 Herbster D ec. 14, 1943V 

